The brain disease is attributed to both symptomatic concussions and asymptomatic subconcussive hits to the head that do not result in symptoms.

While previous research has demonstrated a strong link between the condition and professional football players, prize fighters and extreme sport stars, it now appears CTE is much more widespread than first thought.

A recent study discovered anyone that has played contact sport at any level could be living with the disease, which triggers progressive degeneration of the brain tissue.

After examining 202 deceased former football players - including a combination of high school, college and professional players - CTE was diagnosed in 177 of them.

Even more concerning was the fact 99 per cent of the former NFL players in the study had CTE.

Suicide was the most common cause of death among those suffering mild CTE, with 27 per cent of those involved in the study taking their own lives.

Yet for those with severe CTE, degenerative diseases such as Alzheimer's and Parkinson's disease were more present.

On average those with mild and severe CTE had played football for 13 and 15.8 years, respectively.

Lead author Ann McKee said while it's hard to pinpoint the exact occurrence rate, she suspects the problem was extremely widespread.

"While we still don't know what the incidence is in the general population or in the general population of football players, the fact that we were able to gather this many cases says this disease is much more common than we previously realised," she told NPR.

Ms McKee said many of the families of players involved in the study had expected to see some evidence of CTE.

"Families don't donate brains of their loved ones unless they're concerned about the person. So all the players in this study, on some level, were symptomatic," she said.

The chief of neuropathology at VA Boston Healthcare System said more research needs to done to understand the degenerative brain disease.

"I think any sports organisation that has participants that are exposed to head trauma needs to endorse this research and support it," she said.

"We need a very well-constructed longitudinal study looking at young individuals playing these sports. We need to follow them for decades.

"We need to take measurements throughout their lives and playing careers so we can begin to detect when things start to go wrong. If we can detect early changes, that's when we could really make a difference."

Ms McKee added wasn't willing to condemn contact sport entirely at this stage, but feels like there is a definitely a cause for concern.

"While I'm not willing to say football is doomed and I also am unwilling to make a decision [on a young person playing football] for other individuals ... I think there's a risk to playing football," she said.